Rotary and orbital tools are commonly used in conjunction with an abrasive member to abrade material from a workpiece. Most such tools include a motor, an output shaft for transmitting the rotary motion of the motor, and an abrasive member that is attached to the output shaft. One common abrasive member includes a single, circular abrasive disk that is mounted on a backing pad, typically using pressure sensitive adhesive, hook and loop fasteners, cooperating male and female threaded members, or the like. After the backing pad and abrasive member are connected to an output shaft, the rotating abrasive disk may be urged against a workpiece to abrade material from the workpiece.
Although single, circular abrasive disks are popular for some applications, they tend to lack flexibility near the edge of the disk, which limits their efficacy under circumstances requiring a more flexible abrasive. For example, contoured surfaces may be sanded more effectively with an abrasive member having a flexible edge than with one having a more rigid edge, so that the workpiece is not marred or overcut due to edge cutting by a standard circular disk. Edge cutting refers to excessive abrasion of material from a workpiece due to a stiff abrasive edge.
An improvement over the single, circular abrasive disk is an abrasive sheet member having a main portion and two or more arm portions radially projecting from the main portion. The individual abrasive sheet members are typically of substantially identical geometric configuration (e.g. a main portion and six arm portions, as in FIG. 1; a main portion and two arm portions, as in FIG. 3). As shown in FIG. 1, each individual abrasive sheet member 10 includes opposed major surfaces, one of which includes an abrasive coating 12, a body portion 14 and a plurality of arm portions 16 separated from each other by a constant angle .alpha. with respect to center point 17. The individual arm portions add flexibility to the periphery of individual sheet member 110. Further flexibility may be obtained by forming a plurality of cuts in each of the arm portions to form a plurality of finger portions 20. Because the finger portions 20 are collectively more flexible than the respective arm portion would have been without the cuts therein, the abrasive sheet members are particularly adapted to abrade contoured profiles with a minimum of edge cutting. The cuts in arm portions 16 are generally parallel to each other in each of the arm portions, as shown in FIGS. 1 and 3.
The individual sheet members may be either a coated abrasive or a nonwoven abrasive. The former includes a backing (e.g. cloth, paper, vulcanized fiber, or polymeric film) with abrasive grains bonded thereto by one or more binder coats of phenolic resin, urea-formaldehyde resin, acrylate resin, epoxy resin, aminoplast resin, hyde glue, urethane resin, polyester resin, or a combination thereof. Nonwoven abrasives include a substrate, which may be a porous, fibrous, nonwoven construction and an abrasive comprising individual abrasive particles on one side of the substrate. An example of such a nonwoven abrasive is U.S. Pat. No. 2,958,593 (Hoover et al.), the contents of which are hereby incorporated by reference. The abrasive particles may be made of materials such as fused aluminum oxide, ceramic aluminum oxide, heated treated aluminum oxide, silicon carbide, alumina zirconia, diamond, ceria, cubic boron nitride, garnet, and combinations thereof.
Abrasive sheet members are typically produced individually in a batch die cut operation, which tends to be a relatively slow method of production. In order to produce an abrasive article of suitable size and durability, a plurality of the abrasive sheet members must typically be assembled. Each individual abrasive sheet member has a hole 22 in the center of the main portion, and several like individual abrasive sheet members may be collected and their respective center holes axially aligned. After alignment, which is usually performed manually, each individual abrasive sheet member is manually rotated, or fanned out such that the arm portions of each individual abrasive sheet member are angularly offset by angle .beta., which equals 1/2 of angle .alpha., with respect to the arm portions of each immediately adjacent sheet member, as shown in FIG. 2.
After the individual sheet members have been collected, aligned, and arranged, they may then be secured together to form an abrasive article. One type of releasable fastener that is often used to secure the collection of individual sheet members includes an arbor and retainer, as shown with reference to the present invention in FIG. 7. The arbor 190 usually includes a shaft 192 and a retainer 198 that cooperates with backing member 194 through the aligned holes to retain the collection of individual sheet members. Shaft 192 is adapted to be held by a source of rotary power, and shaft 192 transmits rotary power to the retained collection of individual abrasive members for abrasive application to a workpiece.
Alternatively, a permanent fastener (e.g. a grommet) may be used to hold the individual sheet members together to form an abrasive article. The abrasive article is then retained by an arbor and retainer in much the same manner as the collection of individual abrasive sheet members described above. Examples of such abrasive articles comprising individual abrasive sheet members are available under model numbers 93245 and 93251 from Dynabrade Incorporated of Clarence, N.Y.
The described method of producing the abrasive article is both time consuming and costly. The individual abrasive sheet members must be collected, often by hand, and their respective holes aligned. This process, in addition to being a time consuming one, carries with it the possibility that the holes may be misaligned, which can render the abrasive article difficult to connect to an arbor. Once the holes are aligned, each individual sheet member must be angularly positioned with respect to each adjacent sheet member to produce the desired abrasive article. Because the abrasive articles formed from individual abrasive sheet members may include dozens or even hundreds of individual sheets, this process is also costly and tedious. If the individual sheet members are collected and positioned at the production site, the higher cost is passed on to the consumer. However, if the individual sheet members must be assembled on the job site, the operator must halt the abrading task while collecting, aligning, fanning, and securing the individual sheet members. In view of the time and expense required to form an abrasive article according to the prior art, it is desirable to provide an abrasive article that is easily assembled and used, as well as a method for forming the abrasive article.